Polyalkylene glycol dibenzoates, process of making same and resinous compositions plasticized therewith



fl d rates Pat n POLYALKYLENE GLYCOL DIBENZOATES, PROC- ESS OF MAKINGSAME AND RESINOUS COM- POSITIONS PLASTICIZED THEREWITH Howard F. Reeves,In, Raymond W. Ingwalsou, and

John L. Rose, Jr., Chattanooga, Tenn., assignors to Tennessee Productsand Chemical Corporation, Nashville, Tenn., a corporation of Tennessee NDrawing. Filed July 30, 1953, Ser. No. 371,423 29 Claims. (Cl. 26031.4)

This invention relates to compositions of matter having unusual utilityin plasticizing resinous compositions, particularly polyvinyl chlorideand copolymers, vinyl chloride and vinyl acetate and the like. Moreparticularly, this invention relates to polyalkylene glycol dibenzoatessuch as dipropylene glycol dibenzoate, a process of making the same andresinous compositions plasticized therewith.

Generally, in selecting a compound which would be suitable as aplasticizer, the compound selected should have a high boiling point, lowvolatility, a low freezing point, a mild or pleasant odor, or no odor atall, be compatible with resinous compositions and be non-toxic. Aplasticizer should also be of light color or be colorless, and comprisethe proper degree of polarity.

In the past, dibenzoates of ethylene glycol, diethylene glycol, andtriethylene glycol have been synthesized. The latter two compoundspossess certain characteristics such as high boiling points, goodstability, practically no odor and good compatibility with certainresins, which makes them desirable as plasticizers. On the other hand,the above members of this series are solids at room temperature; thus,it would normally be expected that if a process were devised forproducing the higher members of this glycol series, they would also besolids at room temperature. The dibenzoate of diethylene glycol hasanother disadvantage in that it has the rare quality of possessing twodistinct freezing points, namely 17.2 C. and 29.1 C., the latterfreezing point form being the more stable.

In general, it is very undesirable for a plasticizer to have a highfreezing point where low temperature flexibility is of importance in thefinished plastic item. In addition, solid plasticizers often incurhandling difficulties from the standpoint of having to melt largecontainers of the frozen item. Certain resin compositions are prepared,stored, shipped and used as liquid dispersions of fine resin solids in aplasticizer. When these materials freeze, they must be melted withextreme caution as excessive heat will cause premature gelatin andsolidification and result in complete loss of material.

In the prior art production of glycol esters, the glycol is reacted withan organic acid in the presence of a hydrogen ion catalyst, thefollowing reaction being typical:

Benzolc acid Dlethylene glycol 1? omom-o-oQ O +2H10 5 CHz0H: H

Diethylene glycol dibenzoate A secondary reaction takes place thatsplits or decomposes the product to some extent to yield:

ll CHr0-C l Ethylene glycol dibenzoate tillation of the resulting estersis substantially the only.

way to obtain a pure light colored product. In general, even if heat isapplied, the reaction described above proceeds slowly and the esterstend to darken as the reaction proceeds. When using dipropylene glycolin the above reaction, we have found it necessary,

to accept esterification in the neighborhood of 50% of the theoretical,in order to obtain a reasonably light colored ester. After about tenhours and when approximately 80% of the theoretical water is removed,the

esterification reaction stops and the resulting black viscous materialwhich remains in the reaction zone is unacceptable as a plasticizer.

T o overcome the disadvantages inherent in the process heretoforedescribed, the classic Schotten and Baumann reaction has been used inthe prior art. In this Schotten and Baumann method, poor yields are tobe expected; since, in the reaction the benzoyl chloride hydrolyzes tobenzoic acid; thus, yields of desired esters in the neighborhood of 65%of theoretical yield would be considered good. The resulting ester fromthis process usually has an off-color and odor, and will, in mostinstances, con- 5 tain half-esters which are extremely difficult and insome instances impossible to separate.

The use of pyridine in combination with an aroyl chloride and a hydroxycompound has been proposed; however, this procedure does not lend itselfto large scale production of low cost esters since the pyridine isprohibitive in cost.

By both of the above described prior art methods, it is extremelydiflicult, if not impossible, in most instances, to produce anythingmore than nominal quantities of a sec- 0 ondary glycol ester, i.e. anester from a glycol in which the hydroxy group is attached to asaturated carbon atom in the chain, the carbon containing only onehydrogen atom.

It is a primary object of our invention to provide plas- 5 ticizerswhich have the advantages of the prior art plasticizers andsubstantially none of the disadvantages thereof.

Another object of our invention is to provide new compositions ofmatter.

Another object of our invention is to provide a new process of producingglycol esters which process will provide high yields in substantiallyshort periods of time.

Another object of our invention is to provide a practical andinexpensive process for producing esters of glycols containingsecondary. hydroxyl groups.

Another object of our invention is to provide a process of producingsubstantially pure polyalkylene glycol esters.

Another object of our invention is to provide superior plasticizedresinous products.

Other and further objects and advantages of our invention will. becomeapparent from the following description of embodiments thereof.

Contrary to prior art beliefs and practices, we have been able, througha new process, to produce dibenzoates of glycols which are liquids atroom temperature and have unusual properties as plasticizers. Accordingto our invention, these dibenzoates of glycols are produced byintimately contacting a polyalkylene glycol with an aroyl halide insubstantially equivalent proportions. When commingled, the aroyl halidereacts with all of the hydroxy groups of the glycol and through theevolution of hydrogen halide, which leaves or is withdrawn from thereaction zone substantially at, the rate at which it is formed,substantially complete esterification of the glycol is accomplished.Heat may be applied to the reactants to increase the speed of reactionand it is recommended that the reactants bemaintained at a temperatureof from 80 C. to 125 C. Below approximately 50 C. the reaction proceedsextremely slowly and above about 175 C. there is a tendency for part ofthe aroyl halide to be volatilized with the hydrogen halide. If desired,the reaction zone may be evacuated to induce removal of the hydrogenhalide. In event that either heat or vacuum is applied to the reactionzone, it may be found desirable to provide a reflux condenser to returnthe somewhat volatile aroyl halide to the reaction zone.

Generally, a mole ratio depending on the number of hydroxy groups shouldbe established even though an excess of aroyl halide may be founddesirable. It is also preferable to add the glycol to the aroyl halidesince the halide impurities in the resulting product are diminishedthereby. Further, if large amounts of the glycol are added to therelatively warm chemicals in the reaction zone, there is a tendency forthe aroyl halide to be entrained with the hydrogen halide and to becarried from the reaction zone therewith. After the esterificationreaction is completed and if no vacuum is used during the reaction,small amounts of hydrogen halide gas may be present in the ester and maybe removed therefrom by evacuating the reaction zone while agitating theester. To remove traces of the hydrogen halide and the aroyl halide, theester may then be washed in a mild aqueous alkaline bath. The glycolesters produced according to our invention are insoluble in and heavierthan water, thus these esters may be subjected to many alkaline or waterwashes if desired.

A good yield may also be. accomplished by mixing the. glycol with aroylhalide, at a temperature below which. these reactants will react andthen feeding small increments of the thoroughly commingled reactantsinto a reaction zone where they are heated and reacted. In this event,the hydrogen halide is withdrawn, as: described heretofore.

The esterification. reaction described. above may be illustrated: asfollows:

where R represents an alkylene group or groups, such as methylene,ethylene, ethylidene, etc. and Y represents any interger from 0 up,while X represents a halogen, and R represents an aroyl group or groupsor a substituted aroyl group or groups, for example benzoyl orchlorobenzoyl. It has been found that molecules where Y is as high as 15from suitable plasticizers.

Substituting in the above formula, a dipropylene glycol dibenzoate maybe made from dipropylene glycol and Further, tripropyl'ene glycoldibenzoate may be made from tripropylene glycol and tetra propyleneglycol dibenzoate may be made from tetra propylene glycol, etc. Mixturesof these glycols, as they occur in commerce, work-very smoothly in theabove reaction to yield esters useful as plasticizers. Thus, the newcompounds which we have devised may be expressed as:

where Y represents an integer of 1 to 1'5 and R and R represent phenylor chlorine substituted phenyl. It is equally obvious that thedibenzoates of higher polyethylene glycols or mixtures thereof can bemade by the above: reaction. Instead of benzoyl halide, one may usechlorobenzoyl halides such as meta, ortho, para, 2-4.dichloro, 3-5dichloro benzoyl halide or mixtures thereof. Also, other substitutedbenzoyl halides. such as methyl-, ethyl-, nitro-, etc. benzoyl chloridesmay; be used with such mixtures as benzoyl chloride and chlorobenzoylchloride yielding products of improved properties.

In the above reaction, using a benzoyl chloride or a substituted benzoylchloride, over of theoretical hydrogen chloride is evolved as a puregasand can be readily recovered as a by-product by any prior art method.

Details of the practice of this invention are set forth with respect tothefollowing examples:

EXAMPLE I Ten moles of diethylene glycol (1061.2 grams) were added overan eighty-eight minute period to 20.2 moles (3536 grams). ofmetachlorobenzoyl chloride at 98-105 C. in a three-necked five literflask equipped with. an agitator, a thermometer, a reflux condenser anda. drop.- ping funnel, the diethylene glycol being added through thedropping funnel as the chlorobenzoyl chloride was agitated. The hydrogenchloride gas which formed during the reaction passed through the refluxcondenser and was trapped in water. After all of the diethylene glycolwas added, stirring was continued for 2% hours and the temperature ofthe chemicals within the flask was maintained between 97-135 C. Theproduct was nextbis-meta-chlorobenzoate, a water white liquid was 96.5%

of the theoretical.

EXAMPLE II Ten moles of diethylene glycol (1061.2 grams) were added overan 1% hour period to a mixture of 10.1 moles (1776 grams) ofchlorobenzoylchlorideand 10.1 moles (1423 grams) of benzoyl chloride at105-110 C. in a three-necked five liter flask equipped with an agitator,a thermometer, a reflux condenser and a dropping funnel, the diethyleneglycol being added through the dropping funnel as the chlorobenzoylchloride and benzoyl chloride were agitated. The hydrogen chloride gaswhich formed during the reaction passed through the reflux condenser andwas trapped in water. After all of the diethylene glycol was added,stirring was continued for 4% hours and the temperature of the chemicalswithin the flask was maintained between 106-150" C. The product was nextgiven an alkaline wash (20% Na CO and water followed by a water wash.The product was a water white liquid and consisted of a mixture ofdiethylene glycol dibenzoate, diethylene glycol bis-meta-chlorobenzoateand diethylene glycol benzoate-meta-chlorobenzoate. The yield was 97.5%of the theoretical based on diethylene glycol.

EXAMPLE III Four moles of diethylene glycol (424.5 grams) were addedover a forty-two minute period to 8.16 moles (1146 grams) of benzoylchloride at IOU-107 C. in a threenecked two liter flask equipped with anagitator, a thermometer, a reflux condenser and a dropping funnel, the

diethylene glycol being added through the dropping funnel as the benzoylchloride was agitated. The hydrogen chloride gas which formed during thereaction passed through the reflux condenser and was trapped in water.

After all of the diethylene glycol was added, stirring was continued forfive hours and the temperature of the chemicals within the flask wasmaintained at 102-140 C. The product was next given an alkaline wash(20% Na CO and water) followed by a water wash. The yield of diethyleneglycol dibenzoate, a water white liquid was 98.5% of the theoreticalyield.

EXAMPLE IV Four moles of dipropylene glycol (536.8 grams) were addedover a one and one-half hour period to 8.16 moles (1150 grams) ofbenzoyl chloride at 109 -125 in a three-necked three liter flaskequipped with. an agitator, a thermometer, a reflux condenser and adropping funnel, the dipropylene glycol being added through the dropping135 C. The product was next given an-alkaline wash (20% Na CO and water)followed by a water wash.-

The yield of dipropylene glycol dibenzoate, a water white liquid, was97% of the theoretical yield.

EXAMPLE v Three moles of polyethylene glycol (600 grams, averagemolecular weight 200) were added over a period of twenty-five minutes to6.12 moles (857 grams) of benzoyl chloride at 104-130 C. in athree-necked two liter flask equipped with an agitator, a thermometer, areflux condenser and a dropping funnel, the polyethylene glycol beingadded through the dropping funnel as the benzoyl chloride was agitated.The hydrogen chloride gas which formed during the reaction passedthrough the reflux condenser and was trapped in water. After all of thepoly ethylene glycol was added, stirring was continued for 3 hours andthe temperature of the chemicals within the flask was maintained between104-140 C. The product was next given an alkaline wash (20% Na CO andwater) followed by a water wash. The yield of poly-" ethylene glycoldibenzoate, a water white liquid, was

96% of the theoretical yield.

EXAMPLE VI glycol being added through the'dropping funnel as themeta-chlorobenzoyl chloride was agitated. The hydro-v gen chloride gaswhich formed during the reaction passed. through the reflux condenserand was trapped in water.-

After all of the polyethylene glycol was added, stirring was continuedfor four and one-half hours and the temperature was maintained between96-138" C. The prodnot was next given an alkaline wash (20% Na CO andwater) followed by a water wash. The yield of 'poly-' ethylene glycolbis-meta-chlorobeuzoate, a water white liquid, was 95% of thetheoretical yield.

EXAMPLE VII One mole of polyethylene glycol (300 grams, averagemolecular weight of 300 grams) was added over a fortytwo minute periodto 2.04 moles (287 grams) of benzoyl chloride at 8691 C. in athree-necked one liter flask equipped with an agitator, a thermometer, areflux condenser and a dropping funnel, the polyethylene glycol beingadded through the dropping funnel as the benzoyl chloride was agitated.The hydrogen chloride gas which formed during the reaction passedthrough the reflux condenser and was trapped in water. After all of thepoly- 3 ethylene glycol was added, stirring was continued for threemolecular weight of 400 grams) was added over a one hour period to 2.04moles (287 grams) of benzoyl chlo-j in a three-necked one liter flaskhours and the temperature was maintained between 86'.

135 C. The product was next given an alkaline wash (20% Na CO and water)followed by a water wash.:

The yield of polyethylene glycol dibenzoate, a water white liquid, was97% of the theoretical yield.

EXAMPLE VIII One mole of polyethylene glycol (400 grams, average ride at9S100 C. equipped with an agitator, a thermometer, a reflux condenserand a dropping funnel, the polyethylene glycol being added through thedropping funnel as the benzoyl chloride was agitated. The hydrogenchloride gas which formed during the reaction passed through the refluxcondenser and was trapped in water. After all of the polyethylene glycolwas added, stirring was continued for three hours and the temperaturewas maintained between 97-136" C. The product was next given an alkalinewash (20% Na CO and water) followed by a water wash. The yield ofpolyethylene glycol dibenzoate, a

} water white liquid, was 96% of the theoretical yield.

characteristics of some of these esters being listed below,

Table 1 PHYSICAL CONSTANTS- Sample (names below) 1 2 3 4 5 6 7 BoilingPoint, O. 235 @5 mm. 253 mm. range 1 d. above 300 range 2.5 d. above 300g 225- @1.6mm. mm. 224- 2.3 mm. Freeze, Point, 0,. glass glass below 35-glass in glass glass 25 -40 -3s. 48.

no. No Acidity, mg. KOH/g. Ester- Viscosity, cps. 25 C---" i 4 FlashPoint, 0--

Taken at 0. 1. Dipropylene glycol dibenzoate. 2. Dipropylene glycolbis-chlorobenzoate.

Mixture of diethylene glycol dibenzoate, dlethylene glycolbis-chlorobenzoate and diethylene glycol benzoate-chlorobenzoate.

4. Dibenzoate of polyethylene glycol (molecular weight 200).

5. Bis-chlorobenzoate of; polyethylene glycol (molecular-weight 200). 6.Dibenzoate of polyethylene glycol (molecular weight 300).

7. Dlbenzoate of polyethylene glycol (molecular weight 400).

The glycol esters produced according to our process 20 brittle. Informing a plasticized film, dipropylene glycol were generally found tobe compatible with and to plasticize various resins such as waterinsoluble vinyl resins, water insoluble cellulose esters and waterinsoluble cellulose ethers, the compatibility with specific productsbeing 1. Dipropylene glycol dibenzoate.

2. Dipropylene gylcol bis-chlorobenzoate.

3. Mixture of diethylene glycol dibenzoate, diethylene glycolbischlorobenzoate and diethylene glycol benzoate-chlorobenzoate.

In addition to the. above tabulated resins, the estersas listed in TableH have. plasticizing properties when in admixture with rubberhydrochloride, butadienestyrene copolymers, polymethyl methacrylate,dicarboxylic acid and glycol condensation products and modificationsthereof, and higher molecular weight polymers of isobutylene.

Dipropylene glycol dibenzoate having the empirical formula C H O amolecular weight of 342.3, and a refractive index of 1.53 was tested asa plasticizer by forming films of plastic material containing 100 partsof resin to 50 parts of plasticizer. Using dioctyl phthalate as astandard, under identical conditions, the results are asfollows:

PLASTICIZED FILM TEST In the above film test, DPGDB representsdipropylene glycol dibenzoate while DOP represents dioctyl phthalate.The dipropylene glycol dibenzoate produced according to our inventionand incorporated with a clear plastic as a pl'asticizer provides a cleartranslucent flexible film which requires very low temperature for thefilm to become dibenzoate exhibits remarkable compatible characteristicsas disclosed by Table II hereof, and should preferably comprise.approximately 30% to approximately 40% of the entire weight of theplastic film; however, with as little as 10% of the dipropylene glycoldibenzoate incorporated with a plastic, the plastic becomes pliable,while sweating out of the ester does not occur until the plastic filmcomprises approximately 80% dipropylene glycol dibenzoate. Celluloseacetate films containing 30% by weight of, dipropylene glycol dibenzoateare clear, transparent, free of oiliness and are flexible. Ethylcellulose films containing 30% by weight of dipropylene glycoldibenzoate are exceptionally tough and do not craze or crack on flexing.Dipropylene glycol dibenzoate can be advantageously used innitrocellulose compositions either alone or in admixture with otherplasticizers and stabilizers. Rubber hydrochloride film containing 30%dipropylene glycol dibenzoate is flexible and has good light stabilityproperties. Other liquid glycol dibenzoates produced according to ourinvention exhibit similar properties.

It will be obvious to those skilled in the art that many variations maybe made in the embodiments chosen for purpose of illustration withoutdeparting from the scope of our invention as defined by theappendedclaims.

We claim:

1. Process of preparing; a substantially pure ester consisting ofheating at reaction temperature of above 50 C. and below 175 C. avpolyalkylene glycol selected from the group consisting of polyethyleneand polypropylene glycols. with sufficient aroyl', halide selected fromthe group consisting of benzoyl halide and chlorine substituted benzoylhalide to react with substantially all hydroxyl groups, and removinghydrogen halide formed by the reaction from the reaction zone atsubstantially the rate it is formed until the glycol is substantiallycompletely esterified.

2. The process in claim 1 wherein the esterified glycol is washed withan aqueous alkaline solution to remove any residual hydrogen halide andreacted aroyl halide.

3. Process of preparing substantially pure benzoate esters ofpolyalkyleneglycols consisting of mixing a glycol selected from thegroup consisting of polyethylene glycols and polypropylene glycols witha benzoyl chloride at temperatures belowwhich reaction takes place andcontinuously feeding this mixture to a heated zone maintained at atemperature above 50 C. and below 175 C. where reaction takes place andhydrogen chloride is I removed from the reaction system, removing theesters 5 chloride at a reaction temperature of above 50 C. and

below C. with dipropylene glycol, removing hydrogen chloride byevaporation at substantially the rate it is formed and washing saidesters formed thereby with an aqueous alkaline solution to removeresidual hydrogen chloride and unreacted benzoyl chloride.

5. The process in claim 4 wherein the benzoyl chloride in chlorobenzoylchloride.

6. Process of preparing substantially pure tripropylene glycol benzoateesters comprising heating benzoyl chloride at reaction temperature of80-150 C. with tripropylene glycol, removing hydrogen chloride byevaporation at substantially the rate it is formed and washing saidester with an aqueous alkaline solution to remove residual hydrogenchloride and unreacted benzoyl chloride.

7. Process of preparing substantially pure diethylene glycol benzoateesters consisting of heating benzoyl chloride at reaction temperature of80150 C. with diethylene glycol, removing hydrogen chloride byevaporation at substantially the rate it is formed and washing saidester with an aqueous alkaline solution to remove residual hydrogenchloride and unreacted benzoyl chloride.

8. Process of preparing substantially pure polyethylene glycol benzoateesters consisting of heating benzoyl chloride at reaction temperature of80-150 C. with polyethylene glycol, removing hydrogen chloride byevaporation at substantially the rate it is formed and washing saidester with an aqueous alkaline solution to remove residual hydrogenchloride and unreacted benzoyl chloride.

9. Process of preparing an ester suitable for use as a plasticizerconsisting of heating to a temperature of above 50 C. and below 175 C. abenzoyl halide, adding a polyalkylene glycol selected from the groupconsisting of polyethylene and polypropylene glycols to said benzoylhalide while maintaining said temperature, removing gaseous hydrogenhalide formed by the reaction from the reaction zone at substantiallythe rate it is formed, agitating said benzoyl halide during the additionof said polyalkylene glycol, adding aqueous alkaline solution to themixture to remove the residual hydrogen halide and unreacted benzoylhalide, and thereafter washing the polyalkalene glycol dibenzoate thusformed with water.

10. Compound having the formula:

where y represents an integer of 1 to 15 and R and R represent radicalsselected from the group consisting of phenyl and chlorine substitutedphenyl.

11. Compound as claimed in claim 10 where R and R represent phenyl.

12. Compounds as claimed in claim 10 where R and R represent a chlorinesubstituted phenyl.

13. Compounds as claimed in claim 10 where R represents a phenyl and Rrepresents a chlorine substituted phenyl.

14. A compound: dipropylene glycol dibenzoate.

15. A dibenzoate of a polypropylene glycol.

16. A dizenzoate of tripropylene glycol.

17. A dipropylene glycol benzoate chlorobenzoate.

18. A compound: dipropylene glycol bis-meta-chlorobenzoate.

19. A compound: dipropylene glycol benzoate-metachlorobenzoate.

20. The combination with a plasticizable organic substance selected fromthe group consisting of water insoluble vinyl resins, water insolublecellulose esters and water insoluble cellulose ethers, of a liquidplasticizer having the following formula:

in which y represents an integer of 1 to 15, and R and R representphenyl.

21. The combination as claimed in claim 20 wherein R and R representchlorine substituted phenyl.

22. The combination as claimed in claim 20 Where R represents a phenyland R represents a chlorine substituted phenyl.

23. A plasticized composition comprising polyvinyl chloride anddipropylene glycol dibenzoate.

24. A plasticized composition comprising cellulose acetate anddipropylene glycol dibenzoate.

25. A plasticized composition comprising ethyl cellulose and dipropyleneglycol dibenzoate.

26. A plasticized composition comprising cellulose nitrate anddipropylene glycol dibenzoate.

27. A plasticized composition comprising a vinyl chloride-vinylacetatecopolymer and dipropylene glycol dibenzoate.

28. A plasticized composition comprising polyvinyl chloride anddipropylene glycol bis-chlorobenzoate.

29. A plasticized composition comprising polyvinyl chloride anddipropylene glycol benzoate chlorobenzoate.

References Cited in the file of this patent UNITED STATES PATENTS2,070,331 Derby Feb. 9, 1937 2,480,185 Fife et al Aug. 30, 1949 FOREIGNPATENTS 496,574 Great Britain Dec. '1, 1938 OTHER REFERENCES Heim etal.: Journal of Organic Chemistry, volume 9, pages 299-301 (1944).

Industrial & Engineering Chemistry article by Emerson et al., volume 42,No. 7, July 1950, pages 1431-1433.

20. THE COMBINATION WITH A PLASTICIZABLE ORGANIC SUBSTANCE SELECTED FROMTHE GROUP CONSISTING OF WATER INSOLUBLE VINYL RESINS, WATER INSOLUBLECELLULOSE ESTERS AND WATER INSOLUBLE CELLULOSE ESTERS, OF A LIQUIDPLASTICIZER HAVING THE FOLLOWING FORMULA: